
Analog-to-Digital Converter (ADC)
MC68HC908LJ12 — Rev. 2.1
Technical Data
Freescale Semiconductor
Analog-to-Digital Converter (ADC)
311
ADCO — ADC Continuous Conversion Bit
When set, the ADC will convert samples continuously and update the
ADC data register at the end of each conversion. Only one conversion
is allowed when this bit is cleared. Reset clears the ADCO bit.
1 = Continuous ADC conversion
0 = One ADC conversion
ADCH[4:0] — ADC Channel Select Bits
ADCH[4:0] form a 5-bit field which is used to select one of the ADC
channels when not in auto-scan mode. The five channel select bits
NOTE:
Care should be taken when using a port pin as both an analog and a
digital input simultaneously to prevent switching noise from corrupting
the analog signal.
NOTE:
Recovery from the disabled state requires one conversion cycle to
stabilize.
Table 15-1. MUX Channel Select
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
ADC Channel
Input Select
00000
ADC0
PTA4
00001
ADC1
PTA5
00010
ADC2
PTA6
00011
ADC3
PTA7
00100
ADC4
PTB6
00101
ADC5
PTB7
00110
ADC6
1.2V Bandgap reference
00111
ADC7
↓
ADC28
Reserved
↓↓↓↓↓
11100
11
1
0
1
ADC29
VREFH (see Note 2)
11
1
0
ADC30
VREFL (see Note 2)
11
1
ADC powered-off
NOTES:
1. If any reserved channels are selected, the resulting ADC conversion will be unknown.
2. The voltage levels supplied from internal reference nodes as specified in the table are used to verify the operation of
the ADC converter both in production test and for user applications.